We continued biochemical studies of mammalian DNA replication. proteins. A cDNA for beta-polymerase has been subcloned in expression vectors; the protein has been overproduced in E. coli and purified in mg quantities. In vitro DNA repair activities of the recombinant enzyme are being studied. Genomic DNA spanning the gene for human beta-polymerase was further characterized. The promoter region was studied by detailed deletion mutagenesis using a transient expression system. In other work, we found that beta- polymerase mRNA in cultured rodent cells is induced by DNA alkylating agents, but not by other DNA damaging agents. A tissue survey indicated a higher level of the mRNA in testes than other tissues of the rat.